Joint biodiversity dynamics of above-ground and below-ground communities in Mediterranean urban ecosystems

In urban ecosystems it is generally accepted that anthropogenic pressures, acting at local scale, and landscape heterogeneity, affecting meta-community dynamics, impair biodiversity by promoting biological invasions and biotic homogenization. However, still little is known about biodiversity in urban ecosystems, especially on the joint dynamics of above-ground and below-ground communities, preventing the evaluation of impacts and the definition of sustainable management approaches. The present research aimed at filling this gap by investigating the joint variations in the diversity of herbaceous vegetation and soil microarthropods in Mediterranean urban ecosystems. To this end, the richness, composition and abundance of plants and soil microarthropods were recorded in an urban lawn (Southern Italy), in nearby areas subjected to different land uses (pathways and tree rows). Plants were identified at the species level, and their relative abundances were measured in terms of both number of individuals and biomass; soil microarthropods were identified at different taxonomic levels (classes: Collembola, Pauropoda and Symphyla; orders: Acarina; families: Formicidae), after extraction in MacFadyen funnels, and quantified in terms of number of individuals. Findings highlighted that the local pressures (namely, different land uses) explained a substantial proportion of the spatial variability in the diversity of plants and soil microarthropods, which showed remarkable associations among specific plant and soil microarthropod taxa. In terms of community interactions, the latter suggests that community composition primarily controls the interaction between plants and soil microarthropods, rather than their overall diversity and, thus, the abundance of ecological niches.